Magnesium fuel cells are conventionally known which utilize air (oxygen) as a positive electrode material and metallic magnesium or an alloy thereof as a negative electrode material. For example, Japanese Patent Application Kokai Publication No. 2004-537151 discloses a magnesium fuel cell in which a magnesium alloy containing aluminum and/or tin and/or zinc is used as a negative electrode material. Japanese Patent Application Kokai Publication No. 2010-182435 discloses a magnesium fuel cell in which a magnesium alloy is used as a negative electrode material and an aqueous polyvalent carboxylate salt solution is used as an electrolytic solution.